(CNN) -- An American being held in a Nicaraguan prison said he is innocent and described his treatment in a "hellhole" in an exclusive phone interview with CNN's Anderson Cooper on Thursday.
"I don't know the reason that I'm here," Jason Puracal said. "That's been a mystery from the very beginning. What the motives behind the police and the prosecution have been."
Puracal, a 35-year-old from Washington state, has been behind bars since August 2010, when Nicaraguan authorities raided his real estate office in the coastal tourist city of San Juan del Sur.
In November, a Nicaraguan judge found Puracal guilty of money laundering, drug trafficking and organized crime and sentenced the American to 22 years. But a chorus of supporters say that there is no evidence to support the charges and that Puracal's prosecution was rife with legal mistakes and misconduct.
Puracal's family and supporters have said that while visiting him at La Modelo, they've been shocked to see he's gotten very ill and is disturbingly underweight.
"We're really afraid that his body won't be able to take this much longer," said Janis Puracal, who was allowed to visit her brother in prison several months ago.
Puracal described to Cooper what it's like at La Modelo prison near Managua.
"It's basically a hellhole," he said. "There are concrete cells that are overcrowded.
"I've been in a cell with anywhere from 9 to 12 people in a 12-by-15-foot cell," Puracal continued. "It's hot; it's dirty; it's festy. There's lots of insects, including chiggers and ants and mosquitoes. There's no running water. I have to fight every day to get your two buckets of water. There's no good food. We get rice and beans three times a day, and it has a bicarbonate added to it to make the prisoners feel full, so I can't even eat this stuff.
"I had to go to the hospital," he said. "So, basically, right now, I survive on crackers and peanuts and raisins."
Those fighting to free Puracal include the director of the California Innocence Project, the human-rights attorney who helped win freedom for Burmese Nobel Peace Prize laureate Aung San Suu Kyi and an ex-FBI agent who was one of the early champions of Amanda Knox's innocence.
U.S. Rep. Adam Smith, D-Washington, said in February that Puracal's arrest is tantamount to kidnapping (PDF). Even the three American hikers freed from Iran have spoken out against the American's conviction.
Recently, a special group of independent legal experts with the United Nations declared that Nicaragua was violating international law (PDF) by imprisoning Puracal and that he should be immediately released. Puracal's defense team provided the group's recommendation to CNN.
Since CNN began reporting Puracal's story, it has made numerous attempts on the phone and in person in Nicaragua to obtain comment from officials involved in Puracal's case. Each attempt has been rebuffed.
Cooper asked Puracal whether he thought the U.N. group's opinion would increase the chances that officials in Nicaragua will release him.
"I would hope so, that the administration of Nicaragua would value the independent U.N. opinion about my case," Puracal answered. "However, it's been a couple weeks since that has been publicly released and about a month since Nicaragua has refused that privately, and yet I'm still sitting here."
Puracal went to Nicaragua in 2002, shortly after graduating from college in Washington, to work for the Peace Corps. He stayed there because he fell in love with the country, Janis Puracal said.
He met the woman who would become his wife, a Nicaraguan national, and they had a child.
Puracal developed a successful real estate business in San Juan del Sur and was even featured on the HGTV show "House Hunters International."
He was in his office in 2010 when Nicaraguan authorities burst in with their guns drawn, he told Cooper.
"I was shocked," he said. "I had donated to the police department in San Juan del Sur. And I had interacted with them on a positive basis previously, but when guys in masks and assault rifles stormed into my office, I thought I was being robbed.
"I didn't know what was going on until a plainclothes guy with a badge around his neck came in and asked for me. And then he still didn't tell me for the next two days -- even after they arrested me -- why I was being arrested or for what it was all about."
The Nicaraguan government accused Puracal of being part of a group of drug traffickers, but Puracal's defense team says investigators could not establish links between Puracal and 10 Nicaraguans who were convicted with him.
Jared Genser, a well-known international human rights attorney who helped free Suu Kyi, said Puracal has never met the other defendants, and the co-defendants told the judge in the case that they had never met Puracal.
When Janis Puracal, a lawyer in Seattle, approached Genser with her brother's case, he immediately took it.
"I knew that something was very wrong here" after reviewing the court documents, he said.
The U.N. Working Group on Arbitrary Detention rendered its opinion that Puracal should be freed in response to a petition (PDF) Genser filed this year. The document detailed numerous alleged flaws in the case against his client.
The Working Group doesn't have the authority to force a country to act in response to its opinions, but it can send a strong diplomatic and political message, Genser said.
"The fact that Jason is the only one of more than 3,000 Americans imprisoned abroad (to have the support of the U.N.), the U.N. calling for his release should demonstrate to the Nicaraguan government that its failure to resolve this case quickly will have serious diplomatic consequences," he said.
In response to questions about Puracal's case, U.S. State Department spokesman Mark Toner said several weeks ago that officials are "continuing to work" on Puracal's behalf "through counselor and diplomatic channels."
On Wednesday, Cooper's interview with Puracal was ended abruptly after Cooper asked whether Puracal felt that he was in danger.
Puracal: "Umm ... the guards are telling me I have to go now. But thank you for your ... for your call."
Cooper: "Is there anything you want people to know before you go?"
Puracal: "I am 100% innocent of the crimes I've been accused of, and I can't wait to see my family. And I thank everyone for all their support and their effort."